WAUKESHA, Wis. (CBS 58) -- A controversial Waukesha County Sheriff's detective is resigning - citing personal reasons. 

Joseph Mensah is the former Wauwatosa police officer who shot and killed three people over a five-year stretch. 

He never faced any charges in those cases and resigned from the department in November of 2020. A few months later he was sworn in as a detective for the Waukesha County Sheriff's Department. 

In a statement, the Waukesha County Sheriff's office said "The Waukesha County Sheriff's Office acknowledges the resignation of Detective Mensah. We support Detective Mensah and wish him the best." 

Mensah's resignation is effective at the end of the month.